microemulsions - centurion university

Microemulsions

1

A Concise Presentation

By

Mr. Deepak Sarangi M.Pharm

CONTENTS : Historical background

Definition

Composition of microemulsion

Major goals

Advantages

Disadvantages

Macroemulsion Vs Microemulsion

Types of microemulsions

Preparation methods of microemulsions

Equipments used for the preparation of microemulsions

Formation of microemulsion

Factors affecting microemulsion formation

Evaluation parameters studies

Applications

Marketed preparations

Conclusion

References

omega college of pharmacy. 2

HISTORICAL BACKGROUND :

The microemulsion concept was introduced

as early as 1940’s by Hoar and Schulman

who generated a clear single-phase solution

by titrating a milky emulsion by hexanol.

Schulman and co-worker(1959)subsequently

coined the term microemulsion.

omega college of pharmacy.3

DEFINITION :“ Micro-emulsions is homogenous,

transparent, thermodynamically stable

dispersions of water and oil, stabilized by

a surfactant, usually in combination with a

co-surfactant.”


ALTERNATIVE NAMES :

Microemulsions are also called as,

Transparent emulsion

Swollen micelle

Micellar solution

Solubilized oil


COMPOSITION OF MICRO-EMULSION :

Microemulsions is defined as transparent

dispersion consisting of,

1. Oil

2. Surfactant

3. Co-surfactant

4. Water


MAJOR GOALS :

To delivery of Hydrophilic as well as

Lipophilic drug as drug carriers because

of it’s

1) Improved drug solubilization capacity

2) Long shelf life

3) Easy of preparation and

4) Improvement of bio-availability

omega college of pharmacy.7

ADVANTAGES : Increase the rate of absorption

Increase bio-availability

Helpful in taste masking

Eliminates variability in absorption

Helps in solubilizing lipophilic drugs


DISADVANTAGES : Use of large concentration of surfactant

and co-surfactant necessary for thestabilizing micro droplets.

Limited solubilizing capacity for highmelting substances.

Microemulsion stability is influenced byenvironmental parameters such as,temperature & pH.These parameterschange upon microemulsion delivery tothe patients.


EMULSIONS Vs MICROEMULSIONS :Shape :


MACROEMULSIONS Vs MICROEMULSIONS :

FEATURES MACROEMULSIONS MICROEMULSIONS

Droplet diameter 1-20mm. 10-100nm.

Appearance Most of the emulsions are

opaque(white).

Microemulsions are

transparent.

Stability They are stable but

coalesce finally.

More thermodynamically

stable than macro

emulsions.

Preparation Require intense agitation

for their formation.

Generally obtained by

gentle mixing of

ingredients.

Surfactant

concentration

2-3% by weight. 6-8% by weight.

Interface contact Direct oil/water contact at

the interface.

No direct oil/water contact

at the interface.


TYPES OF MICROEMULSIONS :Microemulsions are of 3 types.They are :

1) O/W Microemulsion

2) W/O Microemulsion

3) Bi-continuous microemulsion


O/W Microemulsion where in droplets are

dispersed in the continuous aqueous phase.

W/O Microemulsion where in water droplets

are dispersed in the continuous oil phase.

Bi-continuous microemulsion where in

micro domains of oil & water are inter

dispersed within the system.

In all the three types of microemulsions,the

interface is stabilized by an appropriate

combination of surfactants and/or co-

surfactants.


PREPARATION METHODS OF MICROEMULSIONS :

Following are the different methods used for

the preparation of the microemulsions :

1) Phase titration method

2) Phase inversion method


PHASE-TITRATION METHOD :1. Dilution of an oil-surfactant mixture with

water.[W/O]

2. Dilution of a water surfactant mixture

with oil.[O/W]

3. Mixing of all components at once, in

some systems, the order of ingredients

addition may determine whether a

microemulsion forms are not.


PHASE-INVERSION METHOD :Temperature range in which an o/w microemulsions

inverts to a w/o type.

Using non-surfactants: polyoxyethylene are verysuspectible to temperature.

with increasing the temperature, thepolyoxyethylene group becomes dehydrated,altering critical packing parameter which results inthe phase inversion.

For ionic surfactants: increasing temperature,increase the electrostatic repulsion between thesurfactant headgroups thus causing reversal of filmcarvature.

Hence, the effect of temperature is opposite to the effectseen with non-ionic surfactants.


EQUIPMENTS USED FOR THE

PREPARATION OF MICROEMULSIONS :

Colloidal mill

Rotorstator

Homogenizer


FORMATION OF MICROEMULSION :

Microemulsion is formed when

The interfacial tension at the o/w inter

phase are brought at very low level.

The interfacial tension is kept at highly

flexible and fluid.


FACTORS AFFECTING MICROEMULSION

FORMATION :

1. PACKING RATIO

2. PROPERTY OF SURFACTANT

3. PROPERTY OF OIL PHASE

4. TEMPERATURE

5. CHAIN LENGTH

6. NATURE OF CO-SURFACTANT


EVALUATION PARAMETERS STUDIES :

1. Phase behaviour

2. Size and shape

3. Rheology

4. Conductivity

5. Zeta potential

6. pH

7. Drug release studies

8. Physical stability study


APPLICATIONS :1) Oral delivery system

2) Parenteral delivery system

3) Ophthalmic delivery system

4) Microemulsions in detergency

5) Microemulsions in cosmetics

6) Microemulsions in foods


MARKETED PREPARATIONS :BRAND

NAME

DRUG COMPANY DOSAGE

FORM

CATEGORY

Douxo

seborrhea

Phyto

sphingosine

Sogeval Spray Emollient

Retamax Retinol Skin health inc., Cream Emollient

White

glow

SPF25 Lotus herbal Cream Emollient

Tray bell Cocoa extract Alcantra Shampoo Cleansing


CONCLUSION : Microemulsions are potentially quite

powerful alernative carrier system fordelivery because of high solubilizationcapacity, transparency, thermodynamicstability, ease of preparation, and highdiffusion and absorption rates through skin,when compared to solvent without thesurfactant system.

A number of factors must be considered whenusing microemulsions as drug delivery systemsuch as surfactant, co-surfactant, oils, pH,HLB, temperature etc.


REFERENCES : The Theory and practice of Industrial

pharmacy., Leon Lacham,Herbert

A.Liberman special indian edition

2009,pg.no: 507-530.

Shaji,J.,Reddy, M.S.; Microemulsion as

drug delivery system,Pharma Times,

2004,pg.no:139-146.

Razdan,R.,Devarajan,P.V.; Microemulsions

Indian Drugs, 2003,pg.no: 139-146.



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microemulsions - centurion university

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